Cyclist of note about to sell his pants (4,9)

'cyclist' is the definition.
(professional cyclist)

'note about to sell his pants' is the wordplay.
I cannot really understand how this works, but
'note' could be 'mark' (synonyms) and 'mark' is found in the answer.
'about' could be 'ca' (abbreviation for 'circa') and 'ca' is present in the answer.
'sell' could be 'vend' (vending is a kind of selling) and 'vend' is located in the answer.
an anagram of 'his' is 'ish' which is present in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).

'of' acts as a link.